Alot of other words, along the same lines as Jim'* thoughts, were the usual language of the peasants of the old world empires, for they were seen as "vulgar". It was well below the royalty to speak like peasants, and the words came to be under a derrogatory light, of sorts.
Popular etymologies agree, unfortunately incorrectly, that this is an acronym meaning either Fornication Under Consent of the King or For Unlawful Carnal Knowledge, the latter usually accompanying a story about how medieval prisoners were forced to wear this word on their clothing.
Deriving the etymology of this word is difficult, as it has been under a taboo for most of its existence and citations are rare. The earliest known use, according to American Heritage and Lighter, predates 1500 and is from a poem written in a mix of Latin and English and entitled Flen flyys. The relevant line reads:
Non sunt in celi quia fuccant uuiuys of heli.
They [the monks] are not in heaven because they f*** the wives of Ely [a town near Cambridge].
Fuccant is a pseudo-Latin word and in the original it is written in cipher to further disguise it.
Some sources cite an alleged use from 1278 as a personal name, John le F***er, but this citation is questionable. No one has properly identified the document this name supposedly appears in and even if it is real, the name is likely a variant of *****, a maker of cloth, fulcher, a soldier, or another similar word.
The earliest usage cite in the OED2 dates from 1503 and is in the form fukkit. The earliest cite of the current spelling is from 1535.
The word was not in common (published) use prior to the 1960s. Shakespeare did not use it, although he did hint at it for comic effect. In Merry Wives of Windsor (IV.i) he gives us the pun "focative case." In Henry V (IV.iv), the character Pistol threatens to "firk" a French soldier, a word meaning to strike, but commonly used as an Elizabethan euphemism for f***. In the same play (III.iv), Princess Katherine confuses the English words foot and gown for the French foutre and coun (f*** and c*nt, respectively) with comic results. Other poets did use the word, although it was far from common. Robert Burns, for example, used it in an unpublished manuscript.
The taboo was so strong that for 170 years, from 1795 to 1965, f*** did not appear in a single dictionary of the English language. In 1948, the publishers of The Naked and the Dead persuaded Norman Mailer to use the euphemism "fug" instead, resulting in Dorothy Parker'* comment upon meeting Mailer: "So you're the man who can't spell f***."
The root is undoubtedly Germanic, as it has cognates in other Northern European languages: Middle Dutch fokken meaning to thrust, to copulate with; dialectical Norwegian fukka meaning to copulate; and dialectical Swedish focka meaning to strike, push, copulate, and fock meaning *****. Both French and Italian have similar words, foutre and fottere respectively. These derive from the Latin futuere.
While these cognates exist, they are probably not the source of f***, rather all these words probably come from a common root. Most of the early known usages of the English word come from Scotland, leading some scholars to believe that the word comes from Scandinavian sources. Others disagree, believing that the number of northern citations reflects that the taboo was weaker in Scotland and the north, resulting in more surviving usages. The fact that there are citations, albeit fewer of them, from southern England dating from the same period seems to bear out this latter theory.
Want to know any other word origins??